1. Field of the Invention
The present invention is directed to a stroke limiter for limiting the stroke of a hydraulic piston by automatically opening the poppet valves located in the piston when the piston has reached its maximum desired stroke.
2. Description of the Prior Art
Large industrial machines such as crawlers are provided with hydraulic cylinders for manipulating a work member. A work member such as a dozer blade is coupled to hydraulic cylinders which raise and lower the blade as desired by the operator. The hydraulic cylinders are relatively conventional and comprise a hollow cylinder in which is mounted a piston having a piston rod attached thereto. By applying pressurized hydraulic fluid to either side of the piston, the piston is driven in one direction or another thereby manipulating the work member which is operatively coupled to the piston rod. The piston is provided with spring biased poppet valves. The poppet valves become unseated when they contact the end wall of the cylinder and as such form a hydraulic pressure relief passage across the piston. The poppet valves are provided so that the piston cannot be driven past its maximum design stroke.
To maximize a crawler's operational range, an owner will at times mount different working members or different blades on the crawler. As these working members or blades have somewhat different uses, their working geometry in relation to the crawler is somewhat different. As such, it may be necessary to replace the cylinders so that the stroke of the cylinder more closely matches the working geometry of the new working member.
One method of overcoming the replacement problem, when a shorter stroke cylinder is needed, is to provide a sleeve that can be slidably mounted about the piston rod. As the piston is extended, the sleeve which is in contact with the end wall of the cylinder prematurely contacts the poppet valves effectively producing a shorter stroke. Some problems associated with the above described sleeves is that they may inadvertently open the poppet valves before the piston has reached the desired stroke because they are free to slide up and down the piston rod. Another problem associated with the sleeves is that the cylinder end cap must be removed from the piston rod before the sleeve can be mounted on the rod.